[TUHS] The origins of portability in C External Inbox Forums

[Douglas McIlroy via TUHS]

Portability of Fortran code was a major theme at Bell Labs. Phyllis
Fox oversaw the creation of the Port library of numerical software,
which became publicly available upon the advent of the internet.

Before the Port library, Stan Brown, Barbara Rider, and Andy Hall had
been central to an ambitious portability effort for Altran, a
symbolic-algebra language. They identified Pfort, a subset of Fortran
that was portable except for issues of data representation. In
particular, Altran implemented multiple-precision integers.

A verifier to assure that Fortran code complied with Pfort was written
in Pfort. The M6 macroprocessor, also written in Pfort, was created to
deal with adjusting Fortran code that depended  on word size or
character code. The Altran compiler itself was written in Pfort
tailored by a set of M6 definitions for each machine architecture.

Of course making C portable was a bigger deal than doing it for
Altran. C had to compile to different instruction sets, while Altran
always compiled to Pfort. But the Altran portability effort certainly
fed into the C project, particularly via Steve Johnson, who worked on
both. One notable congruence is their use of macro preprocessors.

Doug